The Simpsons 20th Anniversary Special – In 3-D! On Ice!, which aired immediately following "Once Upon a Time in Springfield", was assigned production number LABF21 and technically counts as a component of the 20th production season (and of the 21st broadcast season).

The Simpsons Guy (a Family Guy episode), which aired immediately following "Clown in the Dumps", was assigned production number BACX22/BACX23 and technically counts as a component of the 25th production season of The Simpsons and 13th broadcast season of Family Guy. It does not, however, count towards the series' official episode count. Al Jean confirmed on Twitter that the episode's availability on FXX's Simpsons World app is "to be specified"[1] and that they "would love to include it on the Season 26 home and digital release."[2]

The Great Phatsby is a combination of two episodes: The Great Phatsby: Parts One & Two (WABF04 and WABF05), aired as a long episode in two different time slots, one of them where Bob's Burgers would normally be aired.